This application claims the priority of Malaysian patent document PI 2000 3975, filed Aug. 29, 2000, the disclosure of which is expressly incorporated by reference herein.
The present invention relates to a process and apparatus for the continuous coagulation and drying of a rubber latex. In the specification the term xe2x80x9crubber latexxe2x80x9d includes both a natural rubber latex and synthetic rubber latices.
There has previously been proposed and developed a process in which a rubber latex is fed through a coagulator in which the temperature of the latex is raised sufficiently to cause the latex to coagulate to form coagulated rubber. The coagulated rubber is then fed through a dryer which reduces the moisture content of the coagulated rubber to an acceptable level.
In the above-mentioned conventional process, the coagulation of the rubber latex can take several hours, and the drying process can take more than 15 hours.
It is an object of the invention to provide a process and apparatus for the continuous coagulation and drying of rubber latex in which the above-mentioned coagulation and drying times are reduced and there is a more precise control of the coagulation and drying process.
According to one aspect of the invention t here is provided a process for the continuous coagulation and drying of rubber latex in which at stream of the latex is passed through a coagulator to form coagulated rubber. The coagulated rubber stream from the coagulator is introduced into a dryer downstream of the coagulator, and the coagulated rubber is passed through the dryer to dry the rubber. The latex stream in the coagulator is heated by a combination of microwave energy and hot air to cause the latex to coagulate.
The coagulation temperature may be in the range from 30xc2x0 C. to 90xc2x0 C., and preferably the latex stream entering the coagulator may have a thickness in the range from 1.0 mm to 15. 0mm.
The coagulated rubber in the dryer may also be heated by a combination of microwave energy and hot air to dry the rubber, and the rubber may be dried to have a moisture content of less than 1.5%.
The process may also include stretching the coagulated rubber stream as it passes between the coagulator and the dryer, and preferably this coagulated rubber stream is stretched by increasing the speed at which the stream is conveyed to the dryer.
According to another aspect of the invention, an apparatus is provided for the continuous coagulation and drying of rubber latex. The apparatus included a coagulator, a first feeding apparatus to pass a stream of latex through the coagulator to form coagulated rubber, a primary heater operable to provide a combination of microwave energy and hot air to coagulate the latex stream passing through the coagulator, a dryer to receive the coagulated rubber stream from the coagulator, a second feeding apparatus to pass the coagulated rubber stream through the dryer, and a secondary heater to dry. the coagulated rubber passing through the dryer.
The secondary heater may also be operable to provide a combination of microwave energy and hot air to dry the rubber.
The apparatus may also include a stretch unit to stretch the coagulated rubber stream leaving the coagulator before it enters the dryer, and preferably the first and second feeding apparatus are conveyor belts.